<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
.outer {
    width: 500px;
    position: relative;
}
.container {
    width: 30%;
    transform: translate(0, 0);
}
.inner {
    position: fixed;
    margin-top: 100%;
}
    </style>
</head>

<body>
    <div class="outer">
        <div class="container">
            <div class="inner"></div>
        </div>
    </div>
</body>

</html>